A cellulose acetate superior in the balance of hydrophilicity and hydrophobicity has been widely used for industrial purposes as a gas separation membrane, a reversed semipermeable membrane, an ultrafiltration membrane, a precision filtration membrane or the like, as well as a hemodialysis membrane to be used for an artificial kidney (hemodialyzer). When a cellulose triacetate membrane or a cellulose diacetate membrane is used for a hemodialyzer as a hollow fiber membrane for hemodialysis, however, high pressure steam sterilization (e.g. at 120.degree. C. for 20 min) causes deterioration by heat and structural change due to crystallization and orientational crystallization, so that water permeability and permeation of solute are markedly impaired to prohibit application of the high pressure steam sterilization to cellulose acetate membrane.